U.S. Homeland Security Secretary Alejandro Mayorkas said Thursday that a Texas law giving state authorities the power to arrest and deport migrants who have entered the country illegally is unconstitutional.

Mayorkas spoke during a joint news conference with Guatemala President Bernardo Arévalo in the Guatemalan capital.

“It is our strongly held view as a matter of law that SB4 (the Texas law) ... is unconstitutional and it is our hope and confidence that the courts will strike it down with finality,” Mayorkas said.

The Texas law passed last year would allow the state to arrest and deport people who enter the U.S. illegally. The U.S. Justice Department has challenged the law as a clear violation of federal authority.

A three-judge panel of the 5th U.S. Circuit Court of Appeals heard arguments on the Texas law Wednesday, but did not rule. The law is on hold for now.

According to Reuters, Mexico filed a U.S. court brief supporting the Justice Department's opposition to the Republican-backed Texas law.

"Mexico is deeply concerned that SB 4 will be applied in a discriminatory manner and fears that its enforcement will lead to improper harassment, detention, removal, and criminalization of Mexican citizens and individuals of Latino appearance," the document said, according to the news service.